This invention relates to the field of dynamic magnetic information storage and/or retrieval, and particularly to a magnetic tape transport with a rotating head which moves during transducing operation. This movement maintains a flying relationship between the head's transducing gap and the tape's adjacent magnetic recording surface. The head's flying ability is established by a gas bearing, specifically of the hydrodynamic or self-generated type.
Flying heads are well known in the art of scanning rigid magnetic medium such as a rigid magnetic disc. Such an environment is comparable to flying an aircraft a few feet above ground over a hard surface. Consequently, many of the magnetic disc heads use air foil configurations with force biasing to control the head-to-disc flying separation or height. The biasing typically comprises spring or pneumatic loading.
In the art of the flexible magnetic medium, flying heads are also well known. For example, in the magnetic tape art a relatively large, stationary magnetic head transduces the tape in the direction of tape motion. The head is large relative to the tape's lateral dimension or width. Because of this size relationship, the whole width of the tape flies relative to the head, as it passes over the head. Flying has been accomplished in this art by using cylindrically shaped heads, above-atmospheric pressure, and vacuum or below-atmospheric pressure to control the flying height of the entire tape width as it moves across the large stationary head. U.S. Pat. 3,327,916 is an example of such prior art relating to flying heads which are large relative to the flexible magnetic medium.
Another type of flexible magnetic medium is a flexible magnetic recording disc. Two examples of prior art flexible disc devices which include flying heads are one in which the disc is rotated over a rigid backer plate, on a thin film of air which enters the backing plate. A stationary head is then mounted on the backing plate, to protrude into the plane of the disc, and to fly relative thereto. The second example is an apparatus wherein an annular groove is formed in the disc's backing plate. A spherically shaped stationary head extends into the groove. The disc rotation creates hydrodynamic forces causing the head to fly relative to the disc.
The present invention is restricted to that class of flying heads wherein the head is much smaller than the areal dimension of the cooperating flexible magnetic media, be it magnetic tape or a flexible magnetic disc, and to the combination of a spherical surface formed on the head's transducing interface, this surface including at least two parallel surface slots formed in the spherical surface, one on each side of the head's transducing gap, the slots extending in the direction of the relative head/media movement.
In its more specific aspects, the present invention contemplates a rotating head device wherein two spaced and stationary mandrels of the same diameter or cross-section cooperate with an intermediate headwheel.
An alternate construction would be to provide one stationary mandrel and a cooperating rotating mandrel, this rotating mandrel carrying a head thereon, closely adjacent the interface with the stationary mandrel. In this construction the tape is supported adjacent the rotating mandrel by a hydrodynamic and/or hydrostatic air-bearing force.
The flying height of the head defined by the present invention is a function of the slot width and the distance between the slots, the distance parameter being of primary importance. In addition, these slots function to receive tape generated debris and to allow this debris to be flushed away from the head-to-tape interface by the airflow induced by head movement.
While the flying of small dimension heads is known in the prior art, these prior art teachings do not solve the problem of reliably maintaining a uniform, stable, hydrodynamic air film over a relatively large area of the head's surface profile, which area includes the head's transducing gap. The present invention combines a specific surface profile, i.e. generally spherical, with airflow slots running parallel to the direction of head motion. These slots are positioned at least one on each side of the head's gap, to thus center the relatively large area of microinch flying over the gap.
In an embodiment of the present invention, the head is of the well known glass/ferrite type. An additional advantage is achieved with this head by forming at least a portion of the above-mentioned slots so as to relieve or recess the head's glass lines below the spherical profile, thus eliminating a troublesome area of wear and/or contamination. The removal of the glass lines from the head surface profile is an additional advantage in that it operates to reduce residual stress on the head's ferrite gap and thus increases the magnetic permeability of the ferrite. A further advantage of this construction is the enabling of direct measurement of the gap's throat height.
The foregoing and other features, and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawing.